About 120 out of 600 vehicles were out of service Wednesday, the third day of the Muni sickout.

Following a three-day sickout that has infuriated the public, Muni's 1,500 or so operators have found themselves without friends in government, isolated from the broader labor movement and out of options -- thanks in part to a 2010 voter initiative that changed the way transit workers are paid.

Muni service ran at about 70 percent Wednesday, the lightest day of a three-day sickout staged in protest of a labor dispute between the San Francisco Municipal Transportation Agency and its vehicle operators union. Under the City Charter, Muni workers cannot strike.

Union honchos claimed no association with the sickout, which kept about 120 of 600 vehicles out of service Wednesday.

That's a lower number of missed runs than Muni experienced on at least two days in May, according to records. Muni officials were "cautiously optimistic" that today's service would be even closer to normal, agency spokesman Paul Rose said.

However, city officials' patience is beyond exhausted. Unlike with last year's two BART strikes, no prominent elected officials have publicly sided with Muni operators.

One of BART's unions is the politically powerful Service Employees International Union, which is a major force in California politics. Muni's union, Transport Workers Union Local 250-A, has no such clout.

Following calls Tuesday from Mayor Ed Lee and other key elected officials to end the sickout, City Attorney Dennis Herrera filed a complaint Wednesday against Muni's union with state labor officials.

Muni drivers are currently the sixth-best-paid transit operators in the country, with a maximum wage of $29.52 per hour, said John Haley, the SFMTA's transit director. The SFMTA's current contract offer ups that maximum to $32 an hour.

However, increased employee contributions to pensions would lead to a $1.10-per-hour cut in take-home pay, said Local 250-A President Eric Williams.

Muni also suffers from a driver shortage, with over 450 unfilled positions, Rose said.

Voters played a role in the current labor dispute four years ago.

Prior to 2010, a salary survey guaranteed Muni operators the second-highest pay among transit workers in the nation. But that year, voters approved Proposition G, removing the salary survey and sending Muni workers to collective bargaining and then binding arbitration like all other city workers.

There was, however, one major exception. The ballot initiative also inserted language into the arbitration rules that "stack the deck" against worker proposals and make it harder to negotiate, said Jamie Horowitz of the Transport Workers Union's national offices.

Workers rejected the SFMTA's contract offer 1,198-47 last week. Wage and pension terms will now be decided by an arbitrator. Meetings are slated to begin Saturday.